1HCB

ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE

Summary for 1HCB

• Entry DOI: 10.2210/pdb1hcb/pdb
• Descriptor: CARBONIC ANHYDRASE I, ZINC ION, BICARBONATE ION, ... (4 entities in total)
• Functional Keywords: lyase(oxo-acid)
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm: P00915
• Total number of polymer chains: 1
• Total formula weight: 28901.41

Authors

Kumar, V.,Kannan, K.K. (deposition date: 1994-01-07, release date: 1994-04-30, Last modification date: 2024-02-07)

Primary citation

Kumar, V.,Kannan, K.K.
Enzyme-substrate interactions. Structure of human carbonic anhydrase I complexed with bicarbonate.
J.Mol.Biol., 241:226-232, 1994

PubMed Abstract: The structure of HCAI-HCO3- complex has been refined with 10-1.6A X-ray diffraction data to an R-value of 17.7%. The structure reveals monodentate binding of the HCO3- anion at an apical tetrahedral position to the zinc ion. The binding mode and interactions of HCO3- in HCAI differ from that in HCAII. The activity linked H2O/OH- group in the free HCAI is replaced by the hydroxyl group of the bicarbonate anion. This result rules out the rearrangement of the bound HCO3- advocated earlier to explain the microscopic reversibility of the catalysed reaction. From the geometry of the H-bonds between Glu106-Thr199 pair and Glu117-His119 couple, the glutamic acids are expected to be ionized and accept H-bonds from their partners. The product-inhibiton by HCO3- anion is explained on the basis of proton localization on His119 in the Glu117-His119 couple. These results are consistent with the hypothesis that Glu117-His119 tunes the ionicity of the Zn2+ and the binding strength of HCO3- anion. A pi hydrogen bond is observed between a water and phenyl ring of the Tyr114 residue.

PubMed: 8057362
DOI: 10.1006/jmbi.1994.1491

Experimental method

X-RAY DIFFRACTION (1.6 Å)